I. Field of the Invention
The present invention relates to a cold-water dispersible, modified starch characterized by its gelling properties, and a process for its preparation. This invention also relates to food systems containing such a starch.
II. Description of the Prior Art
It is often desirable to prepare food systems which have a set or gel texture, such as pie fillings, puddings and jellies. Many types of food systems of this description contain gelling agents and must be cooked to effect gelation. Common gelling agents used in the past for this purpose are agar, gelatin, corn starch, pectin, carrageenin, algin, and combinations of locust-bean gum and xanthan gum. In addition, starches derived from, e.g., corn, potato, tapioca, and wheat which are acid-converted to a certain water fluidity level will retrograde to a gel when cooked.
An example of a food product which requires cooking to effect gelation is the conventional starch-based pudding, which generally consists of an ungelatinized starch, flavorings, sweetening agents, etc. Such puddings are prepared for consumption by adding milk, cooking until the starch is gelatinized, pouring the cooked mixture into a bowl or individual serving dishes, and cooling and/or refrigerating.
There are, however, certain disadvantages associated with food systems of this type. In addition to the fact that cooking of the food system is necessary to impart the gel mixture thereto, many of the gelling agents used in these systems require specific conditions. Thus, for example, gelatin can be used only after dissolution in very hot water, and typical pectins for use in jellies require about 65% sugar solids to produce a gel.
The remaining types of known food systems which have a set or gel texture form a gel without cooking. Most of these products are milk-based and consist of pregelatinized (i.e., cold-water dispersible) starch, one or more setting agents, which are usually phosphate salts (e.g., tetrasodium pyrophosphate), and flavoring, sweetening, and coloring agents. The set or gel properties of these food systems are obtained from the interaction of the phosphate salts with the casein and calcium ion provided by the milk, and not with the starch ingredient in the formulation. The pregelatinized starch functions as a viscosity builder or thickening agent, but is not the prime factor in the developement of the gel structure of the prepared food system.
The major drawback of these uncooked, so-called "instant", food formulations is that they do not have the firm gel structure of the cooked formulations, i.e., they do not cut as cleanly with a spoon; and their texture, rather than being smooth, is generally described as "grainy" in both appearance and "mouth-feel" characteristics. Moreover, the setting salts are not operative at low pH or in non-milk-based food systems.
U.S. Pat. No. 3,583,874 discloses a starch composition suitable as gelling agent in instant puddings, which comprises a blend of a pregelatinized, defatted starch and a granular, preswollen starch having a water fluidity in a certain range.
A cold-water dispersible, modified tapioca starch which forms a gel when dispersed in cold water is taught in U.S. Application Ser. No. 1,720 filed Jan. 8, 1979 to Chung Wai Chiu et al. This starch product is obtained by drum-drying a tapioca starch which has been converted to a specified water fluidity and reacted with a crosslinking agent to give Brabender viscosity parameters within a selected range. It is taught therein that if the starch is simply crosslinked and drum dried without having been converted to a fluidity starch, a product having gelling properties is not obtained.